1. Field of the Invention
This invention relates to a radiation image storage panel, and more particularly, to a radiation image storage panel comprising a support and at least one phosphor layer provided thereon which comprises a binder and a stimulable phosphor dispersed therein.
2. Description of the Prior Art
For obtaining a radiation image, there has been conventionally employed a radiography utilizing a combination of a radiographic film having an emulsion layer containing a photosensitive silver salt material and a radiographic intensifying screen.
As a method replacing the above-described radiography, a radiation image recording and reproducing method utilizing a stimulable phosphor as described, for instance, in U.S. Pat. No. 4,239,968, has been recently paid much attention. In the radiation image recording and reproducing method, a radiation image storage panel comprising a stimulable phosphor (stimulable phosphor sheet) is used, and the method involves steps of causing the stimulable phosphor of the panel to absorb radiation energy having passed through an object or having been radiated by an object; exciting the stimulable phosphor with an electromagnetic wave such as visible light and infrared rays (hereinafter referred to as "stimulating rays") to sequentially release the radiation energy stored in the stimulable phosphor as light emission; photo-electrically processing the emitted light to give an electric singnal; and reproducing the electric signal as a visible image on a recording material such as a radiographic film or on a recording apparatus such as CRT.
In the above-described radiation image recording and reproducing method, a radiation image can be obtained with a sufficient amount of information by applying a radiation to the object at considerably smaller dose, as compared with the case of using the conventional radiography. Accordingly, this radiation image recording and reproducing method is of great value especially when the method is used for medical diagnosis.
The radiation image storage panel employed in the above-described radiation image recording and reproducing method has a basic structure comprising a support and a phosphor layer provided on one surface of the support. Further, a transparent film is generally provided on the free surface (surface not facing the support) of the phosphor layer to keep the phosphor layer from chemical deterioration or physical shock.
The phosphor layer comprises a binder and stimulable phosphor particles dispersed therein. When excited with stimulating rays after having been exposed to a radiation such as X-rays, the stimulable phosphor particles emit light (stimulated emission). Accordingly, the radiation having passed through an object or having been radiated by an object is absorbed by the phosphor layer of the radiation image storage panel in proportion to the applied radiation dose, and a radiation image of the object is produced in the radiation image storage panel in the form of a radiation energy-stored image (latent image). The radiation energy-stored image can be released as stimulated emission (light emission) by applying stimulating rays to the panel. The stimulated emission is then photo-electrically processed to convert to electric signals, so as to produce a visible image from the radiation energy-stored image.
It is desired for the radiation image storage panel employed in the radiation image recording and reproducing method to have a high sensitivity and to provide an image of high quality (sharpness, graininess, etc.).
For enhancement of the sensitivity of a radiation image storage panel, it has been known to provide a light-reflecting layer between a support and a phosphor layer of the panel. For instance, the light-reflecting layer is provided by vapor-deposition of a metal such as aluminum, lamination of a metal foil such as an aluminum foil, or coating of a binder solution containing a white powder such as titanium dioxide.